Reactions of 5-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione with primary and secondary alkylamines †

The reactions of 5-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione with primary alkylamines (2 equiv.) in CH2Cl2 at rt gave 5-[(alkylamino)(cyano)methylidene]-2,2-dimethyl-1,3-dioxane-4,6-diones (2) in excellent yields. Similarly, the reactions with ethylenediamine, trans-1,2-diaminocyclohexane, 2-aminobenzylamine, and 2-aminoethanol under the same conditions afforded 5-(imidazolidin-2-ylidene)- (3a), 5-(octahydro-2H-benzimidazol-2-ylidene)- (3b), 5-[3,4-dihydroquinazolin-2(1H)-ylidene]- (3c), and 5-(1,3-oxazolidin-2-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-diones (3d) in moderate to excellent yields. Interestingly, the reactions with secondary acyclic dialkylamines under the same conditions yielded 5-(4-dialkylamino-5H-1,2,3-dithiazol-5-ylidene)-2,2-dimethyl-1,3-dioxane-4,6-diones (7) (0–60%), 6-carbamoyl-5-oxo-5H-furo[2,3-d][1,2,3]-dithiazoles (8) (0–28%), sulfur, and bis(dialkylamino) sulfides (R2N–Sx–NR2), whereas the reactions with cyclic amines, i.e., pyrrolidine and piperidine, gave the corresponding methylidene-Meldrums acid derivatives 9, analogous to 2, as major products. Mechanisms are proposed for the formation of these products.